Not Applicable
Not Applicable.
The present invention relates to internal combustion engines. In particular, the present invention relates to a cross-flow cylinder head having improved cooling.
Internal combustion engines generally have a cylinder extending from a crankcase. The cylinder receives a reciprocating piston which closes off one end of the cylinder. A cylinder head closes off the opposing end of the cylinder, and defines a combustion chamber in the cylinder between the head and piston.
Fuel and combustion air is guided into the cylinder combustion chamber by a intake passage. The flow of fuel and combustion air through the intake passage is controlled by an intake valve. The intake valve can be opened to allow the flow of fuel and combustion air, and can be closed to block the flow of fuel and combustion air into the combustion chamber.
Hot exhaust gasses formed in the combustion chamber are exhausted through an exhaust passage which guides the exhaust gasses out of the combustion chamber. The flow of exhaust gasses out of the combustion chamber is controlled by an exhaust valve. The exhaust valve can be opened to allow gasses to flow out of the combustion chamber, and can be closed to prevent the flow of gasses out of the combustion chamber.
Combustion of the fuel and air in the combustion chamber creates a tremendous amount of heat which raises the temperature of the cylinder, cylinder head, and surrounding engine components. This heat can cause metallic parts, such as the cylinder and cylinder head to deform which is detrimental to the engine performance. In order to maintain engine performance, cooling the engine is an important aspect of engine design.
One known method for cooling engine is to circulate a cooling liquid in passageways surrounding the cylinder and cylinder head to extract heat from the metal parts. The liquid is routed through a radiator which extracts heat from the liquid prior to being recirculated past the maintains heat generating portions of the engine. Liquid cooled engines, however, are expensive compared to engines which depend upon air flowing past heat generating parts for cooling.
Known air-cooled engines, such as disclosed in U.S. Pat. No. 4,570,584, employ a fan which forces cooling air over the cylinder and cylinder head to cool the engine. The engine disclosed in U.S. Pat. No. 4,570,584 also incorporates a cross-flow cylinder head which has an intake passage and an exhaust passage which are aligned vertically and open in opposite directions. The exhaust passage is shielded from the forced cooling air generated by the fan, and thus does not benefit significant from the cooling ability of the forced air.
It would therefore be advantageous if an improved cylinder head was provided which takes full advantage of the cooling air generated by a fan.
The present invention provides an internal combustion engine which has improved cylinder head cooling. The engine includes a crankcase and a cylinder having a proximal end and a distal end. The proximal end of the cylinder is fixed to the crankcase. A cylinder head covers the distal end of the cylinder, and includes an intake passage and an exhaust passage. The intake passage opens toward a first side of the cylinder head for guiding combustible material to the cylinder. The exhaust passage opens toward a second side of the cylinder head which is opposite to the first side, and guides exhaust gasses away from the cylinder. An intake valve for controlling the flow of combustible material into the cylinder barrel through the intake passage includes an intake valve stem which extends through the cylinder head. An exhaust valve for controlling the flow of exhaust gasses out of the cylinder barrel through the exhaust passage includes an exhaust valve stem extending through the cylinder head. The intake valve stern and the exhaust valve stem define a central valve region therebetween. An intake rocker arm, is pivotally mounted relative to the cylinder head. The intake rocker arm has a first end engaging the intake valve stem and a second end extending toward the first side of the cylinder head, wherein pivotal movement of the intake rocker arm axially moves the intake valve stem to move the intake valve between an open position and a closed position. An exhaust rocker arm is pivotally mounted relative to the cylinder head. The exhaust rocker arm has a first end engaging the exhaust valve stem and a second end extending toward the second side of the cylinder head, wherein pivotal movement of the exhaust rocker arm axially moves the exhaust valve stem to move the exhaust valve between an open position and a closed position. An intake push rod adjacent to the first side of the cylinder head extends parallel to the intake push rod, and engages the intake rocker arm to pivot the intake rocker arm. An exhaust push rod adjacent to the second side of the cylinder head extends parallel to the exhaust push rod, and engages the exhaust rocker arm second end to pivot the exhaust rocker arm.
A general objective of the present invention is to improve the cooling of the cylinder head. This objective is accomplished by locating the push rods adjacent opposite sides of the cylinder head to clear out the central valve region between the valve stems, and allow more cooling air to flow through the region.